The present inventions relate to optical fibers and, more particularly, to optical fibers having at least one buffer layer.
Optical fibers are used to transmit information signals, for example, voice, video, and/or data information. Optical fibers are relatively fragile silica-based filament-like strands and require protection to preserve the optical performance thereof. For example, optical fibers require protection from macro-bending and/or micro-bending to inhibit undesired optical performance degradation.
In order to meet these requirements, optical fibers may include a protective layer therearound. For example, an optical fiber can have a buffer layer therearound to protect the optical fiber during bending. The buffer layer may be either loosely or tightly disposed around the optical fiber. A loose buffered optical fiber generally has a relatively small gap between the optical fiber and the buffer layer, for example, a gap of about one hundred microns, whereas a tight buffered optical fiber has a relatively smaller or no gap therebetween. An example of a loose buffered fiber is disclosed in U.S. Pat. No. 5,917,978, which is incorporated herein by reference. Additionally, an interfacial layer may completely circumscribe the optical fiber preventing contact between the buffer layer and optical fiber coating, for example, to promote the stripability of the buffer layer from the optical fiber.
Buffered optical fibers can be used, for example, as a buffered optical fiber interconnect assembly that includes a buffered optical fiber and at least one optical connector attached thereto. The buffered optical fiber interconnect assembly can, for example, be used to connect photonic devices. The optical performance of a buffered optical fiber interconnect assembly can be measured, for example, by measuring an insertion loss therein. Insertion loss is a measure of a fraction of the signal light that is lost in the interconnect assembly and is, generally, measured in decibels (dB). In general, insertion loss results in a weaker optical signal and is therefore undesirable. Additionally, in certain connector applications, light can be lost if the end faces of the fibers are separated; therefore, the end faces of the fibers should also be maintained in contact within specifications. Fiber-to-fiber separation also implies an insertion loss due to Fresnel reflections at one of the two glass end interfaces.
The formation of the buffer layer is conventionally accomplished through an extrusion process where the buffering material is melted at a relatively high temperature and extruded over the optical fiber that passes through, for example, a cross-head die. After the buffering material is extruded over the optical fiber, the buffered optical fiber passes through a cooling water trough. When the buffering material such as a polyvinyl chloride (PVC) cools, shrinkage of the buffering material can occur. Shrinkage of the buffer layer can result in undesirable compressive axial stress that can cause undesirably high strains in the optical fiber, which in turn can cause undesirable optical performance degradation.
Additionally, there are other sources of buffer layer shrinkage that may cause degradation in optical performance. For example, in the field, a buffered optical fiber interconnect assembly can also experience relatively large environmental temperature and/or humidity variations. Such variations can result in, for example, buffer layer expansion and contraction. The expansion and contraction of the buffer layer can cause tensile and compressive forces to be transferred to the optical fiber(s) within the interconnect assembly, thereby resulting in undesired optical degradation in the interconnect assembly.
The present invention is directed towards a buffered optical fiber having a core, a cladding and at least one coating, and a buffer layer generally surrounding the optical fiber, wherein the buffer layer has a portion thereof generally contacting a portion of the at least one coating, the buffer layer having an average shrinkage of about 3 mm or less from a first end of the buffered optical fiber.
The present invention is also directed to a buffered optical fiber including a buffer layer generally surrounding the optical fiber, and the buffered optical fiber being a portion of an interconnect assembly, wherein the interconnect assembly has an average maximum delta insertion loss of about 0.04 dB or less at a reference wavelength of about 1625 nm during a thermal cycling test that cycles the temperature between a minimum of xe2x88x9240xc2x0 C. and a maximum of 85xc2x0 C.
The present invention is further directed to a method of manufacturing a buffered optical fiber including paying off at least one optical fiber, and extruding a buffer layer around the at least one optical fiber, the buffered optical fiber has a portion thereof generally contacting a portion of the at least one coating of the at least one optical fiber, wherein the buffer layer has an average shrinkage of about 3 mm or less from a first end of the buffered optical fiber.
The present invention is still further directed to a buffered optical fiber including at least one optical fiber, and a buffer layer generally surrounding the optical fiber, wherein the buffer layer has an average shrinkage of about 0.5 mm or less from a first end of the buffered optical fiber.
The present invention is also directed to a buffered optical fiber including at least one optical fiber, and a buffer layer generally surrounding the optical fiber, wherein the buffer layer has an average strip force of about 5 Newtons or less when a 50 cm length of the buffer layer is stripped from an end of the buffered optical fiber.